The overall goal of this pilot project is to determine whether female rhesus monkeys compete for access to male rhesus monkeys around the time of ovulation, in circumstances where access to males is limited. This study was designed to follow up a previous study in Olive baboons, which showed that female-female aggression was increased around the time of ovulation, to establish if this behavior occurs selectively in Olive baboons or can be seen across primate species. This summer and fall 20 adult female rhesus monkeys living in corral #1 were observed for 10 minutes each day, using the focal animal method. All behaviors were recorded. Each day a stool sample was collected for each monkey, for measurement of fecal steroid levels, to assess ovarian activity. Fecal steroid levels are currently being assayed, the observational part of this study has been completed. Fecal steroid levels in daily samples will allow determination of the time of ovulation and will allow evaluation of the hypothesis that female-female aggression increases at ovulation in settings where the number of male monkeys is limited.